Mariano de Leon Regaliza (born November 18, 1958), also known as Julio Diaz, is a versatile film and television actor in the Philippines. He received the Best Actor Gawad Urian Award nomination for his performance in Takaw Tukso (1986).
Diaz did movies such as Sinner Or Saint (1984) with Claudia Zobel, Paano Tatakasan Ang Bukas? (1988) with Dina Bonnevie, Kailan Ka Magiging Akin? (1990) with Janice de Belen, Aliwan Paradise (1992), Bayani (1992), Sakay (1993) with Tetchie Agbayani, The Flor Contemplacion Story (1995) with Nora Aunor, Segurista (1996) with Michelle Aldana, Sana Pag-ibig Na (1998) with Angel Aquino, Hubad Sa Ilalim Ng Buwan (2000) with Klaudia Koronel, Balahibong Pusa (2001) with Rica Peralejo, and Lapu-Lapu (2002) with Lito Lapid.
He also appeared in films like Batanes (2007) with Iza Calzado, Serbis (2008) with Gina Pareno, Kinatay (2009) with Coco Martin, Biyaheng Lupa (2009) with Jacklyn Jose, and 24K (2009).